[Metal Manipulator]

I was filling some holes in a truck frame build and after I was done welding one of the holes but still had the gun pointing at the weld the weld had a nipple grow on it. I chiseled it off and had a crater underneath of it. Using 75/25 gas ,frame was wire brushed to remove rust. Any Ideas?

[Poland308]

Not uncommon. I would grind deeper into the weld. It may be filled with porosity. There by being a compromised weld. Posible causes would be gas flow issues, metal contamination, or even contaminated wire.

[cj737]

Another outside possibility is that the frame is sealed and you welded up the last possible vent hole. The accumulated gas/heat from welding has to go somewhere- blow out. This is not likely on a truck frame, but, in certain conditions, it is a real possibility.

Just something to bear in mind while you work-

[Mike Westbrook]

Very common I've found if you weld it like tracing the petals of a flower and not like a spiral it helps greatly I think by going around the ring and then capping the center it accidentally creates an air pocket that blows out like welding a sealed container

[Metal Manipulator]

Another outside possibility is that the frame is sealed and you welded up the last possible vent hole. The accumulated gas/heat from welding has to go somewhere- blow out. This is not likely on a truck frame, but, in certain conditions, it is a real possibility.

Just something to bear in mind while you work-

Frame is an open channel.

[Metal Manipulator]

Very common I've found if you weld it like tracing the petals of a flower and not like a spiral it helps greatly I think by going around the ring and then capping the center it accidentally creates an air pocket that blows out like welding a sealed container

Thanks, I never thought about that happening.